ProfileInfo.cpp revision a5370172b64bed5daf8e2869d7bf7cb52f80d6b7 
1//===- ProfileInfo.cpp - Profile Info Interface ---------------------------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file was developed by the LLVM research group and is distributed under
6// the University of Illinois Open Source License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file implements the abstract ProfileInfo interface, and the default
11// "no profile" implementation.
12//
13//===----------------------------------------------------------------------===//
14
15#include "llvm/Analysis/Passes.h"
16#include "llvm/Analysis/ProfileInfo.h"
17#include "llvm/Pass.h"
18#include "llvm/Support/CFG.h"
19#include <set>
20using namespace llvm;
21
22// Register the ProfileInfo interface, providing a nice name to refer to.
23namespace {
24  RegisterAnalysisGroup<ProfileInfo> Z("Profile Information");
25}
26
27ProfileInfo::~ProfileInfo() {}
28
29unsigned ProfileInfo::getExecutionCount(BasicBlock *BB) const {
30  pred_iterator PI = pred_begin(BB), PE = pred_end(BB);
31
32  // Are there zero predecessors of this block?
33  if (PI == PE) {
34    // If this is the entry block, look for the Null -> Entry edge.
35    if (BB == &BB->getParent()->front())
36      return getEdgeWeight(0, BB);
37    else
38      return 0;   // Otherwise, this is a dead block.
39  }
40
41  // Otherwise, if there are predecessors, the execution count of this block is
42  // the sum of the edge frequencies from the incoming edges.  Note that if
43  // there are multiple edges from a predecessor to this block that we don't
44  // want to count its weight multiple times.  For this reason, we keep track of
45  // the predecessors we've seen and only count them if we haven't run into them
46  // yet.
47  //
48  // We don't want to create an std::set unless we are dealing with a block that
49  // has a LARGE number of in-edges.  Handle the common case of having only a
50  // few in-edges with special code.
51  //
52  BasicBlock *FirstPred = *PI;
53  unsigned Count = getEdgeWeight(FirstPred, BB);
54  ++PI;
55  if (PI == PE) return Count;   // Quick exit for single predecessor blocks
56
57  BasicBlock *SecondPred = *PI;
58  if (SecondPred != FirstPred) Count += getEdgeWeight(SecondPred, BB);
59  ++PI;
60  if (PI == PE) return Count;   // Quick exit for two predecessor blocks
61
62  BasicBlock *ThirdPred = *PI;
63  if (ThirdPred != FirstPred && ThirdPred != SecondPred)
64    Count += getEdgeWeight(ThirdPred, BB);
65  ++PI;
66  if (PI == PE) return Count;   // Quick exit for three predecessor blocks
67
68  std::set<BasicBlock*> ProcessedPreds;
69  ProcessedPreds.insert(FirstPred);
70  ProcessedPreds.insert(SecondPred);
71  ProcessedPreds.insert(ThirdPred);
72  for (; PI != PE; ++PI)
73    if (ProcessedPreds.insert(*PI).second)
74      Count += getEdgeWeight(*PI, BB);
75  return Count;
76}
77
78
79
80//===----------------------------------------------------------------------===//
81//  NoProfile ProfileInfo implementation
82//
83
84namespace {
85  struct NoProfileInfo : public ImmutablePass, public ProfileInfo {};
86
87  // Register this pass...
88  RegisterPass<NoProfileInfo>
89  X("no-profile", "No Profile Information");
90
91  // Declare that we implement the ProfileInfo interface
92  RegisterAnalysisGroup<ProfileInfo, true> Y(X);
93}  // End of anonymous namespace
94
95ImmutablePass *llvm::createNoProfileInfoPass() { return new NoProfileInfo(); }
96